Burning questions for endangered black cockatoos

The gregarious Carnaby’s cockatoo (Calyptorhynchus latirostris) is such a common sight in Perth that it is easy to forget they are endangered and that the urban and agricultural expansion of south-western Australia has removed the bulk of their habitat. How we manage their remaining habitat will have important consequences for the species’ survival.

South-western Australia is a global biodiversity hotspot that has undergone extensive habitat loss from agricultural and urban development. Less than 30 percent of the original vegetation now remains. As a consequence of this habitat loss, the endemic Carnaby’s cockatoo has experienced widespread loss of nesting and feeding habitat and is considered endangered under the IUCN Red List, and Australian federal and state legislation.

Leonie Valentine and colleagues have been studying the Carnaby’s cockatoo and how their remaining habitat around Perth is managed. Fire management practices influence the availability of food for the cockatoos, particularly seeds produced by Banksia species.

To understand how fire influences food availability in the banksia woodlands, in a recent paper (Valentine et al 2014) we:

1) examined how time since fire influences plant and cone densities of the two dominant native woodland food species, Banksia attenuata and Banksia menziesii;

2) estimated the number of Carnaby’s cockatoos that would be supported in different post-fire aged banksia woodlands, and

3) estimated the number of Carnaby’s cockatoo that could be supported with the current distribution of post-fire banksia woodland habitat.

Food resources are influenced by time since fire and may be manipulated by altering burning patterns. The research predicted that higher numbers of Carnaby’s cockatoos would be supported in vegetation aged between 14 – 30 years since fire, peaking in vegetation aged 20–25 years. The current distribution of post-fire aged vegetation within this area (>60 percent burnt within the last 7 years) is predicted to support only 25 – 35 per cent of the estimated number of birds reliant on the area.

Importantly, this would involve retaining greater areas of woodland burned with less frequency. Current fire management is focused, understandably, on human and asset protection as a priority for prescribed burning.

If management of landscapes for improved persistence of threatened species is also considered important, then complex tradeoffs may have to be considered. The research has proven useful for decisions relating to offsets and as input to population viability modelling.